【作者】 张勇；

【导师】 欧宗瑛； 吕德成；

【作者基本信息】 大连理工大学 ， 机械设计及理论， 2002， 博士

【摘要】 医学图象三维重建及可视化技术的研究内容涉及到数字图象处理、计算机图形学、计算机视觉以及医学等多学科领域。本文对以三维表面重建的原理和方法为主的相关技术及其在虚拟骨折外科手术规划和手术仿真教学实验系统中的应用进行了研究，研究内容主要包括三维空间中断层图象间的插值、三维重建目标区域的边界轮廓提取、三维表面重建及模型处理、实体几何模型与三维表面模型间的相互转化以及模型间的碰撞检测技术。 本文首先进行了断层图象插值的研究。提出了一种基于对象灰度概率知识引导的对应点匹配的灰度插值算法，解决了传统灰度插值的不同种对象物质交界处的模糊问题；对于只关心物体边界和重构目标形态信息的情况，介绍了当相邻断层上的对应轮廓线的形状不相似，位置差异大时，利用改进的轮廓加权平均算法进行轮廓形变插值的方法。 然后对三维重建目标区域的轮廓提取进行了研究。对于基于轮廓线的表面重建，利用主动轮廓模型(Active Model，又称Snake Model)来完成断层图象上目标轮廓的提取，可以获得单象素连通的封闭的目标边界轮廓；针对基于体素的表面重建中实施了分割后的体数据，提出了一种基于主动轮廓模型完成二值图象中轮廓跟踪记录的方法，可以对同属于重建目标的内外邻接多区域进行正确和准确的边界轮廓跟踪，使得在跟踪当前轮廓时不会跨越到相邻轮廓，且主动轮廓的精度可以根据参数交互决定，尤其是能够在主动轮廓成长的同时主动定义轮廓关键点。 在由断层图象重建三维表面模型的问题中，本文研究了重建的原理和方法以及对重建模型的处理。首先分析了连接轮廓线法中需解决的关键问题。采用基于全局的柱体生长法来判断断层间轮廓的相互对应关系；针对轮廓线表面重建中的难点问题—分叉问题，提出了一种基于主动轮廓模型的过渡轮廓构造方法，这种方法从物体主动生长这一角度出发考虑过渡轮廓的构造，能够产生综合两断层上轮廓特征的过渡轮廓，是一种基于全局性高层信息的有效轮廓构造算法；利用相邻轮廓线同步前进法进行轮廓拼接。然后在分析轮廓投影关系特性的基础上，给出“连接表面投影区域”的概念以及一种基于投影的体数据转化表面重建方法，选择Marching Tetrahedras(MT)算法进行基于体素的等值面重建，并根据重建的要求对MT算法进行改进。最后提出了一种基于Delaunay三角剖分的骨骼模型的任意骨折模拟方法。 本文还对实体几何模型和三维表面模型间的相互转化进行了研究。研究了实体几何模型向三维表面模型的转化，针对手术规划及仿真教学系统中的医疗器械模型，提出了一种利用三维实体造型系统构建实体模型，然后转化为本文虚拟系统所支持的表面模型的方法，能够方便、精确和参数化地建立模型；针对断层扫描图象，给出了基于CT图象反求技术进行实体几何造型的主要步骤，以使骨骼模型能够在本研究所开发的特征造 大连理工大学博士学位论文型系统3D M。defer中得到进一步的处理。 最后研究了三维模型间碰撞检测及基于快速检测和响应的虚拟骨折半自动复位接合。为了增强虚拟系统的真实感以及引导骨骼模型的正确接合和器械的合理置入，本文分析和研究了提高碰撞检测速度的主要方法。针对临床常见的腿骨（包括股骨、胚骨或排骨）骨不连骨折，提出了一种快速的断骨模型复位接合方法，其中通过减少包围盒数量降低了碰撞计算量；同时，针对层次包围盒的树形数据结构，提出了一种基于工作包围盒缓存的碰撞检测加速方法，使碰撞对能够尽快被检测到。更多还原

【Abstract】 The techenolgy of visualization of medical imagings is related to the research fields of digital image processing, computer graphics, computer vision and medcine etc. This dissertation studies the techniques of geometry reconstruction including slice-imagings interpolation in 3D space, extraction of reconstrction target contours, surface reconstruction from planar contours, transformation between reconstrucion model and 3D solid model and collision detection of models. A prototype system of virtual fracture orthepedic surgery planning and simulated trainning is developed.The reconstruction is implemented from isotropic volume data. Slice-imagings interpolation can creat new slices. This dissertation presents a gray-level matching interpolation method based on object gray-level distribution probability knowlege, through which we can get more clear scene at the boundary between different matters than that in traditional interpolation methods. With respect to non-similar shapes or no superposition of corresponded contours on adjacent slices and concave contours, this dissertation introduces a method based on variant shape-based interpolation.The reconstruct region should be extracted befor 3-D reconstruction. For reconstruction from contours, this dissertation uses Active Contour Model(Snake Model) to check the boundary contours. The algorithm can generate single, continuous and close contours quickly. For reconstruction from voxel, this dissertation presents an algorithm to trace the boundary contours from segmented regions based on Active Contour Model.The algorithm can trace the contours of inter and outer connected multi-regions correctly and accurately, and can prevent tracing from jumping out to the neighbor region, also can define the contour precision and contour key points actively as snake is growing up.This dissertation mainly engages in the research of the theories and techniques of 3-D reconstruction and processing of reconstructed models. Firstly, the key techniques of reconstrction from contours are analized. Cylinder growing method is used to determine the linking relationships of contours between slice-images. Branching problem is a difficulty in surface reconstruction from slice contours. This dissertation proposes an algorithm to solve the problem by constructing transition contours using Active Contour Model. The algorithm considers the transition contours construction as a growing process, so it is based on higher layer knowlege and can ensure that transition contours are similar to trunk contours and branch contours, and also reconstructed transition surfaces at branch points are smooth. The contours are connected using adjacent contours synchronous marching algorithm. Secondly,inthis dissertation also introduces a new concept of "Connected Surface Projection Region ",and proposes a new algorithm for surface reconstruction based on projection. The zero isosurface is extracted using MT(Marching Tetrahedras) algorithm. In accordance with the intersection feature between isosurface and voxel, this dissertation made improvement in MT algorithm. Lastly, an arbitrary bone model fracture simulation method based on Delaunay triangulation is presented.This dissertation also studies the transformation between reconstructed surface model and solid model. For surgery tools models, this dissertation presents an algorithm to transform models constructed in solid modeling system to the developed virtual system in which surgery tools models can be constructed conveniently, accurately and parameterizely.The constructed models can have high level third dimension effect. For slice-imagings, this dissertation gives an algorithm for rebuilding solid model from triangulated patch surface model and the rebuilding processing function as an important function in reverse engineering has been added to 3D-Modeler system, which is a feature solid modeling system developed by CAD Lab of DUT, so the reconstruted bone model can be further processed in the CAD system.To enhance the immersion of the vir更多还原